1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) apparatus and a method for driving the same, and more particularly, to an LCD apparatus in which at least two overshoot voltages are applied to a pixel electrode in response to a change of grayscale data of a frame to improve a response time as well as display quality and a method for driving the LCD apparatus.
2. Description of the Related Art
LCD apparatuses are thinner and lighter and draw much less power than cathode ray tubes. They are used in laptop computers, mobile phones and many other electronic devices.
Recently, new technologies have been developed to improve the display quality of LCD apparatuses. One of them is a DCC (Dynamic Capacitance Compensation) technology. The DCC technology improves a response speed of LC (Liquid Crystal) molecules by compensating a grayscale voltage of a current frame with a previous grayscale voltage and a current target grayscale voltage.
Another new technology is Patterned Vertical Alignment (PVA). PVA mode LCD apparatuses control the switching behavior of LC (Liquid Crystal) molecules by forming an opening pattern in a pixel electrode (or transparent electrode) or a common electrode or by creating fringe fields, thereby providing a wide view angle.
Although the DCC and PVA technologies improve the display quality of LCD apparatuses, LCD apparatuses still have pattern blinking problems. As LCD apparatuses become larger, the pattern blinking appears more.
FIG. 1 is a graph showing the response time of a PVA mode LCD apparatus before and after performing a DCC method. As shown in an “x” marked line, a rising time is slow at a middle level of grayscale, i.e., until seven or eight frames are passed, when the DCC is not performed. The slow rising time can be improved by performing the DCC, as shown in a “•” marked line. However, there are still problems such as luminance deterioration or appearance of residual images. For example, when PVA mode LCD apparatuses display a motion picture, the motion picture blinks due to the change of luminance.
FIG. 2A is a graph showing the data voltages of a PVA mode LCD apparatus before and after performing a DCC method. FIG. 2B is a graph showing the luminance of a PVA mode LCD apparatus before and after performing a DCC method.
When the DCC method is not performed in PVA mode LCD apparatuses, an arrangement of LC molecules is gradually changed even when a level of grayscale is abruptly changed from a low level to a high level. That is, as shown the “x” marked lines of FIG. 2A and 2B, the arrangement of LC molecules corresponding to the high level of grayscale is completed after two or three frames have passed and a luminance is gradually increased. Although, as shown in the “•” marked lines of FIGS. 2A and 2B, the LC molecules are arranged rapidly, that is, the response time is reduced, by performing the DCC method, the luminance of PVA mode LCD apparatus drops again after temporarily increasing, because the LC molecules tends to return to an original arrangement. Thus, LCD apparatuses have pattern blinking, resulting in deteriorating display quality.